In recent years suitcases have been built with two to four wheels permanently attached to the bottom of the suitcase for ease in pulling them instead of carrying them. These built in wheels are usually about an inch and a half in diameter. Such wheels work fine is long as the suitcases are being pulled along a smooth surface, such as in an airport, or a parking lot. However, when such suitcases have to be towed along a rough surface, such as a cobblestone street, the wheels are too small and they are generally ineffective in reducing the effort required to pull the suitcase along.
An obvious way to overcome this difficulty would be to increase the diameter of the wheels, but this would create severe problems when the suitcases have to be lifted or moved into a storage area on an airplane or bus, because the wheels would protrude so far that rough handling would damage the wheels and the wheels on the various suitcases in the storage area of an airplane or bus could become interlocked, creating great difficulty for the baggage handlers.
To overcome this problem, the larger diameter wheels would have to be removably attached to the suitcase. In the past suitcases have been constructed in such a way that the wheels could be retracted into recesses formed in the suitcase. However if larger diameter wheels are used to overcome the problem of pulling the suitcase over a rough surface, a substantial volume of the suitcase would be occupied in providing recesses for storing the wheels at the expense of the carrying capacity of the suitcase.
The concept of retracting wheels on suitcases into recesses formed into the suitcase is old as shown by the patents to McIntyre No. 2,596,578, Stilger No. 2,925,283, Lyngby No. 4,097,955, and Quinton No. 2,472,491. But the wheels disclosed in these patents where small in diameter and were no better then the current suitcases when the suitcase was pulled over rough ground.
Another approach to the concept of attaching wheels to a suitcase was to mount the wheels on a bracket which was either permanently or removably attached to the outer surface of the suitcase. This is exemplified by the patent to Hokkanen No. 1,413,852, Brower No. 2,919,138, Davis No. 2,661,220, Haft No. 4,217,675, and Walker No. 3,997,038.
All of the above described patents used small diameter wheels because they were not concerned with problems encountered when pulling the suitcase over rough surfaces. Of the above described group of patents, the patent to Walker No. 3,997,033 best lends itself to the use of large diameter wheels because as shown in FIG. 3, of Walker the axle carrying the wheels extended beyond the sides of the suitcase so the wheels 10 mounted on the axle 18 could be as large as desired. The axle 18 on which the wheels were was press fit into a slot 20 formed in the mount or bracket 13. However as admitted by Walker on column 2 lines 64 to 68, press fitting the axle into the slot was not satisfactory when the suitcase was being handled roughly, as by baggage handlers or when being towed over rough ground, because the axle structure would then separate from the suitcase. Moreover, in the course of time continued use of the Walker Structure shown in FIG. 3 would gradually widen the slot 20 so that the axle 18 would no longer be press fit in the slot and the wheel-axle assembly would tend to separate from the suitcase eventually.
To prevent this from happening, Walker disclosed another embodiment as shown in FIG. 7. In this embodiment, holes were bored through the mounts, and the axle was inserted through the bore, so that the axles could not separate from the suitcase. However this increased the cost and complexity of the axle structure.
Nonetheless, very many older suitcases still being used do not have any wheels attached to them and a structure generally like the one shown by Walker in FIG. 3 would be an economical way to provide these older suitcases with wheels. However, as admitted by Walker, the simple structure shown in FIG. 3 permits the separation of the axle structure from the suitcase when the suitcase is handled roughly or being towed over a rough surface, and as stated above, the fit between the axle and the slot 20 would become loose as the suitcase is used over a course of time.
Because of the problems inherent in the Walker structure, an important object of this invention is to improve on the teachings of Walker and provide an inexpensive and simple way to attach a bracket on the bottom of the suitcase where the bracket has a slot for receiving the axle, but where instead of relying on a pressfit between the axle and the slot in the mount or bracket to hold the axle in the slot, the axle is provided with means which positively releasably lock the wheel carrying axle into the slot on the mounts or brackets attached to the bottom of the suitcase.